Conjugated organic polymers, due to the delocalization of π-electrons, exhibit attractive optical and nonlinear optical properties and there is considerable interest in development of efficient sensors and sensing matrices utilizing such conjugated polymers. An example of this class of polymers is polydiacetylenes (PDAs). PDA-based sensors are intensely investigated due to their unique color changing properties upon stimulation. For example, when PDAs are exposed to thermal or mechanical stress, the polymers undergo a change in color from blue to red. Although not fully understood, it is widely accepted that this change in color is brought about by the conformational changes in the PDA backbone. Thus, the dark blue color of the polymers gradually shifts to red color depending on the amount of the stress exposed. This colorimetric property of PDAs has been exploited for making PDA-based sensors to detect changes in temperature, pH, ions, solvents, volatile organic compounds (VOCs), ligand-receptor interactions and the like.
Although PDAs are valuable for the development of a wide range of embedded sensors, there exists a problem in the synthesis of PDAs. Current diacetylene polymerization conditions include heating to high temperatures, at which most organics decompose, or exposing to high intensity UV, X-ray and γ-ray irradiations. Many of these methods fail to produce good yields of high purity PDAs due to limitations such as failure of reactions to undergo completion, decomposition of polymers during the polymerization and most critically, imperfect alignment of the monomers in the solid state pre-polymerization. It is often noticed that the newly synthesized polymer materials are damaged due to side chain breaks as a result of UV or gamma-ray irradiation. The current synthesis of PDAs through solid-state processes often produces poor yields due to irregular conjugated backbones. Thus, an efficient and simple synthesis of PDAs suitable for large scale production is desired.